System, method, and article of manufacture for determining parameter values associated with an electrical grid

ABSTRACT

A system, method, and article of manufacture for determining parameter values associated with an electrical grid in accordance with an exemplary embodiment is provided. The electrical grid has a point of interconnection where the electrical grid is electrically coupled to a power source. The method includes measuring real power at the point of interconnection of the electrical grid to obtain a plurality of real power values. The method further includes measuring reactive power at the point of interconnection of the electrical grid to obtain a plurality of reactive power values. The method further includes measuring a voltage at the point of interconnection of the electrical grid to obtain a plurality of voltage values. The method further includes estimating at least one parameter value associated with the electrical grid utilizing the plurality of real power values, the plurality of reactive power values, and the plurality of voltage values, and a mathematical estimation technique.

BACKGROUND OF THE INVENTION

A wind farm utilizes a plurality of wind turbines to generate electricalpower. The wind farm is generally electrically coupled at a point ofinterconnection to an electrical grid.

A control system is utilized to control the electrical output from awind farm to meet utility requirements at the point of interconnectionwith an electrical grid of a utility company. However, a well-knownproblem associated with the conventional control system is that thecontrol system is unable to determine electrical grid parameter valuesthat cannot be directly measured such as a grid resistance value, a gridreactance value, and a grid voltage value assuming an infinite bus size.

The inventors herein have recognized a need for an improved controlsystem and method for that can determine parameter values associatedwith an electrical grid.

BRIEF DESCRIPTION OF THE INVENTION

A method for determining parameter values associated with an electricalgrid in accordance with an exemplary embodiment is provided. Theelectrical grid has a point of interconnection where the electrical gridis electrically coupled to a power source. The method includes measuringreal power at the point of interconnection of the electrical grid toobtain a plurality of real power values. The method further includesmeasuring reactive power at the point of interconnection of theelectrical grid to obtain a plurality of reactive power values. Themethod further includes measuring a voltage at the point ofinterconnection of the electrical grid to obtain a plurality of voltagevalues. The method further includes estimating at least one parametervalue associated with the electrical grid utilizing the plurality ofreal power values, the plurality of reactive power values, and theplurality of voltage values, and a mathematical estimation technique.

A system for determining parameter values associated with an electricalgrid in accordance with another exemplary embodiment is provided. Theelectrical grid has a point of interconnection where the electrical gridis electrically coupled to a power source. The system includes ameasurement device configured to measure real power at the point ofinterconnection of the electrical grid to obtain a plurality of realpower values. The measurement device is further configured to measurereactive power at the point of interconnection of the electrical grid toobtain a plurality of reactive power values. The measurement device isfurther configured to measure a voltage at the point of interconnectionof the electrical grid to obtain a plurality of voltage values. Thesystem further includes a controller operably communicating with themeasurement device. The controller is configured to estimate at leastone parameter value associated with the electrical grid utilizing theplurality of real power values, the plurality of reactive power values,and the plurality of voltage values, and a mathematical estimationtechnique.

An article of manufacture in accordance with another exemplaryembodiment is provided. The article of manufacture includes a computerstorage medium having a computer program encoded therein for determiningparameters values associated with an electrical grid. The electricalgrid has a point of interconnection where the electrical grid iselectrically coupled to a power source. The computer storage mediumincludes code for measuring real power at the point of interconnectionof the electrical grid to obtain a plurality of real power values. Thecomputer storage medium further includes code for measuring reactivepower at the point of interconnection of the electrical grid to obtain aplurality of reactive power values. The computer storage medium furtherincludes code for measuring a voltage at the point of interconnection ofthe electrical grid to obtain a plurality of voltage values. Thecomputer storage medium further includes code for estimating at leastone parameter value associated with the electrical grid utilizing theplurality of real power values, the plurality of reactive power values,and the plurality of voltage values, and a mathematical estimationtechnique.

Other systems and/or methods according to the embodiments will become orare apparent to one with skill in the art upon review of the followingdrawings and detailed description. It is intended that all suchadditional systems and methods be within the scope of the presentinvention, and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an electrical power generation systemhaving a wind farm and an electrical grid in accordance with anexemplary embodiment;

FIGS. 2-4 are flowcharts of a method for controlling the wind farm ofFIG. 1 in accordance with another exemplary embodiment;

FIGS. 5-6 are flowcharts of a method for controlling the wind farm ofFIG. 1 in accordance with another exemplary embodiment;

FIG. 7 is a schematic of an exemplary signal response of a measuredoutput voltage level (Vpoi) and a desired output voltage level (Vr) ofthe wind farm;

FIG. 8 is a schematic of an exemplary signal response of a desired netpower command (Q_(C)) utilized to control the wind farm;

FIGS. 9 and 10 are schematics of exemplary signal responsescorresponding to first and second power values (θ₁), (θ₂) utilized tocontrol the wind farm;

FIG. 11 is a flowchart of a method for determining parameters associatedwith an electrical grid;

FIG. 12 is a schematic illustrating estimated grid reactance values andgrid resistance values; and

FIG. 13 is a schematic illustrating estimated grid voltage values.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, an electrical power generation system 10 forgenerating electrical power is illustrated. The electrical powergeneration system 10 includes a wind farm 11 electrically coupled to anelectrical grid 12. The electrical grid 12 is utilized to transferelectrical power from the wind farm 11 to electrical loads. Inalternative exemplary embodiments, the electrical power generationsystem 10 can include at least one of micro-turbines, solar cell arrays,and conventional electrical generators, to replace the wind farm 11.

The wind farm 11 is provided to generate electrical power utilizing windenergy. The wind farm 11 includes wind turbines 14, 15, 16, a collectorsystem 18, a transformer 20, wind turbine controllers 24, 26, 28, ameasurement device 30, and a main controller 32. It should be noted thata number of wind turbines utilized in the wind farm 11 can vary. Forexample, the number of wind turbines in the wind farm 11 can be greaterthan three wind turbines or less than or equal to three wind turbines.

The wind turbines 14, 15, 16 are provided to generate voltages andcurrents utilizing wind energy. The wind turbines 14, 15, 16 areoperably controlled utilizing the wind turbine controllers 24, 26, 28,respectively, which communicate with the wind turbines 14, 15, 16,respectively.

The wind turbine controllers 24, 26, 28 are configured to generatecommand signals which control operation of the wind turbines 14, 15, 16,respectively. Further, the wind turbine controllers 24, 26, 28 areprovided to measure operational parameters associated with the windturbines 14, 15, 16 respectively. The wind turbine controllers 24, 26,28 operably communicate with the main controller 32.

The collector system 18 is electrically coupled to the wind turbines 14,15, 16 and routes voltages and currents from each of the turbines to thepower transformer 20. The power transformer 20 receive the voltages andcurrents from the wind turbines 14, 15, 16 and outputs a voltage and acurrent having desired characteristics onto the electrical grid 12. Forexample, the power transformer 20 can output a voltage having a desiredamplitude and a current having a desired amplitude onto the electricalgrid 12.

The measurement device 30 is electrically coupled to a point ofinterconnection 19 between the transformer 20 and the electrical grid12. The measurement device 30 is configured to measure electricalparameters associated with the electrical grid. For example, themeasurement device 30 is configured to measure a voltage level (Vpoi) atthe point of interconnection 19, a real power level (Pn) at the point ofinterconnection 19, and a reactive power level (Qn) at the point ofinterconnection 19. It should be noted that the measurement device 30can measure parameters on either side of the transformer 20.

The main controller 32 is provided to control operation of the windturbines 14, 15, 16 based on measured or estimated parameter values atthe point of interconnection 19 associated with either the wind farm 11or the electrical grid 12. The main controller 32 is configured togenerate command messages that are received by the wind turbinecontrollers 24, 26, 28 for controlling operation of the wind turbines14, 15, 16, respectively. The main controller 32 includes a centralprocessing unit (CPU) 40, a read-only memory (ROM) 42, a volatile memorysuch as a random access memory (RAM) 44 and an input/output (I/O)interface 46. The CPU 40 operably communicates with the ROM 42, the RAM44, and the I/O interface 46. The computer readable media including ROM42 and RAM 44 may be implemented using any of a number of known memorydevices such as PROMs, EPROMs, EEPROMS, flash memory or any otherelectric, magnetic, optical or combination memory device capable ofstoring data, some of which represent executable instructions used bythe CPU 40. Further, the I/O interface 46 operably communicates with thewind turbine controllers 24, 26, 28.

Referring to FIGS. 2-4, a method for controlling the operation of thewind farm 11 will now be explained. The method can be implementedutilizing software algorithms stored in a computer storage medium andexecuted by the main controller 32 and the wind turbine controllers 24,26, and 28. It should be noted that in alternative exemplaryembodiments, the foregoing method could also be implemented to controlone or more micro-turbines, solar cell arrays, and fossil-fuelelectrical generators, instead of the wind farm 11.

At step 60, the measurement device 30 transmits a first signalindicative of an output voltage of the wind farm 11 to the maincontroller 32.

At step 62, the main controller 32 receives the first signal anddetermines a measured output voltage level (Vpoi) of the wind farm 11based on the first signal.

At step 63, the main controller 32 calculates a target output voltagelevel (Vr) utilizing the following equation:

${V_{r} = {\int{\left( {{{- \frac{1}{T_{r}}} \cdot V_{r}} + {\frac{1}{T_{r}}V_{C}}} \right){\mathbb{d}t}}}},$where

-   -   (Tr) corresponds to a predetermined time constant set by an        operator;    -   (Vr) corresponds to a target output voltage of the wind farm 11;        and    -   (Vc) corresponds to the desired steady-state output voltage        value of the wind farm 11.        It should be noted that in an alternate exemplary embodiment,        instead of utilizing the foregoing equation to calculate (Vr),        the following equation may be utilized to calculate (Vr):        V_(r)=V_(C).

At step 64, each wind turbine controller in the wind farm 11 transmits asecond signal to the main controller 32 indicating whether a respectivewind turbine is operational or not operational. For example, the windturbine controllers 24, 26, 28 transmit second signals to the maincontroller 32 indicating whether wind turbines 14, 15, 16 respectivelyare operational or not operational. A wind turbine is operational whenthe wind turbine generates electrical power (e.g., real or reactivepower) that is transmitted through the transformer 22 to the electricalgrid 12.

At step 66, the main controller 32 receives each of the second signalsand determines a number of operational wind turbines in the wind farm 11based on the second signals.

At step 68, the main controller 32 calculates a voltage error value(Verror) utilizing the following equation: Verror=Vr−Vpoi, where (Vr)corresponds to a desired output voltage level of the wind farm 11.

At step 70, the main controller 32 calculates an integral gain value(Kiv) utilizing the following equation:

${{Kiv} = \frac{Vpoi}{{Xgrid} \cdot {Twv}}},$where

-   -   (Xgrid) corresponds to a known or estimated impedance of the        electrical grid 12; and    -   (Twv) corresponds to a desired time response to the wind farm        11.

At step 72, the main controller 32 calculates a first power value (Q₁)utilizing the following equation: Q₁=∫(K_(iv)·V_(error))dt, when adesired net power command (Q_(C)) is in a range between an upper limitvalue (Qmax) and a lower limit value (Qmin). Alternately, the maincontroller 32 calculates the first power (Q₁) utilizing the followingequation: Q₁=∫(0)dt when (Q_(C)) is not in the range between the upperlimit value (Qmax) and the lower limit value (Qmin).

At step 74, the main controller 32 calculates a proportional gain value(Kpv) utilizing the following equation:

${{Kpv} = {\frac{{{Xwtg}/N} + {Xcollector} + {Xgrid}}{{Kqi}/N}{Kiv}}},$where (Xwtg) corresponds to an internal impedance of a wind turbine;

-   -   (N) corresponds to a number of operational wind turbines;    -   (Xcollector) corresponds to an impedance of the collector system        18 of the wind farm 11;    -   (Xgrid) corresponds to an impedance of the electrical grid 12;    -   (Kqi) is a gain value utilized by a wind turbine controller.

At step 76, the main controller 32 calculates a second power value (Q₂)utilizing the following equation:

${Q_{2} = {\int{\left( {{{- \frac{1}{Tv}}Q_{2}} + {\frac{K_{pV}}{T_{v}}V_{error}}} \right){\mathbb{d}t}}}},$where (T_(V)) corresponds to a predetermined time constant that istypically smaller than the desired closed loop voltage response timeinterval.

At step 78, the main controller 32 generates a desired total reactivepower command (Qtotal) for the wind farm utilizing the followingequation:Q _(total) =Q ₁ +Q ₂.

At step 80, the main controller 32 generates desired net power command(Qc) for each wind turbine 11 in the wind farm 11 utilizing thefollowing equation:

$Q_{c} = \frac{Q_{total}}{N}$when Q_(c) is in a range between the upper limit value (Qmax) and thelower limit value (Qmin).

At step 82, the main controller 32 transmits the desired net reactivepower command (Qc) to each wind turbine controller of the wind farm 11to induce the wind farm 11 to generate an output voltage that approachesthe desired output voltage level (Vc) at the point of interconnection19. After step 82, the method returns to step 60.

Referring to FIGS. 5-6, another method for controlling the operation ofthe wind farm 11 will now be explained. The method can be implementedutilizing software algorithms stored in a computer storage medium andexecuted by the main controller 32 and the wind turbine controllers 24,26, and 28. It should be noted that in alternative exemplaryembodiments, the following method could also be implemented to controlone or more micro-turbines, solar cell arrays, and fossil-fuelelectrical generators, instead of the wind farm 11.

At step 90, the measurement device 30 transmits a first signalindicative of an output voltage of a wind farm 11 to the main controller32.

At step 92, the main controller 32 receives the first signal anddetermines a measured output voltage level (Vpoi) of the wind farm 11based on the first signal.

At step 94, the main controller 32 calculates a target output voltagelevel (Vr) utilizing the following equation:

${V_{r} = {\int{\left( {{{- \frac{1}{T_{r}}} \cdot V_{r}} + {\frac{1}{T_{r}}V_{C\;}}} \right){\mathbb{d}t}}}},$where

-   -   (Tr) corresponds to a predetermined time constant set by an        operator;    -   (Vr) corresponds to a target output voltage of the wind farm 11;        and    -   (Vc) corresponds to the desired steady-state output voltage        value of the wind farm 11.        It should be noted that in an alternate exemplary embodiment,        instead of utilizing the foregoing equation to calculate (Vr),        the following equation may be utilized to calculate (Vr):        V_(r)=V_(C).

At step 96, the main controller 32 calculates a voltage error value(Verror) utilizing the following equation: Verror=Vpoi−Vr.

At step 98, the main controller 32 calculates a first power value θ₁utilizing the following equation: θ₁=∫(−y₁·V_(error)·V_(r))dt when thedesired net power command (Qc) is in the range between the upper limitvalue (Qmax)and the lower limit value (Qmin). Alternately, the maincontroller 32 calculates the first power (Q₁) utilizing the followingequation: Q₁=∫(0)dt, when (Q_(C)) is not in the range between the upperlimit value (Qmax) and the lower limit value (Qmin), where

-   -   (y₁) corresponds to a gain value set by the operator to obtain        the desired closed loop response behavior; and    -   (Vr) corresponds to a target output voltage level of the wind        farm 11.

At step 98, the main controller 32 calculates a second power value θ₂utilizing the following equation: θ₂=∫(−y₂·V_(error)·V_(poi)−ρ·θ₂)dt,where

-   -   (y₂) corresponds to a gain value set by the operator to obtain        the desired closed loop response behavior; and    -   ρ corresponds to a constant value set by the operator to obtain        the desired closed loop response behavior.

At step 102, the main controller 32 generates the desired net reactivepower command (Qc) for each wind turbine in the wind farm 11 utilizingthe following equation: Q_(C)=θ₂·V_(poi)+θ₁·V_(r), where (Q_(C)) is inthe range between the upper limit value (Qmax) and the lower limit value(Qmin).

At step 104, the main controller 32 transmits the desired net powercommand (Qc) to each wind turbine controller of the wind farm 11 toinduce the wind farm 11 to generate an output voltage that approachesthe desired output voltage level (Vc). After step 104, the methodreturns to step 90.

Referring to FIGS. 7-10, the exemplary signal responses 116, 118correspond to a first power value θ₁ and a second power value θ₂ as afunction of time. The first power value θ₁ and second power value θ₂ areutilized to calculate a desired net power command (Qc). The exemplarysignal response 114 corresponds to the net power command (Qc) to inducethe measured output voltage level (Vpoi) at the point of interconnection19 to approximate the target output voltage level (Vr). As shown, theexemplary signal response 112 corresponds to the output voltage level(Vpoi) that closely approximate the exemplary signal response 110.

A brief explanation of the mathematical equations for estimatingparameter values associated with the electrical grid 12 will now beexplained. A plurality of measurements at the point of interconnection19 are utilized to estimate parameter values associated with theelectrical grid 12. For example, a set of “n” data measurement values ofa real power level (Pn), a reactive power level (Qn), and an gridvoltage level (Vn) also referred to as (Vpoi) obtained at the point ofinterconnection 19, is used to determine parameter values for thesimplified model of the electrical grid 12. The simplified model of theelectrical grid 12 is defined by a phasor voltage (V_(g)·e^(jθ))indicative of a positive sequence voltage of an infinite bus in theelectrical grid 19 and an impedance (Z_(g)=r+jx) where “r” correspondsto a resistance value associated with the electrical grid 19 and “x”corresponds to a reactance value associated with the electrical grid 19.The relationship between these two terms can be stated mathematicallyutilizing the following equation:

${P_{n} + {jQ}_{n}} = \frac{V_{n}^{2} - {{V_{n} \cdot V_{g}}{\mathbb{e}}^{{- j}\;\theta}}}{r - {jx}}$

By separating the real and complex terms of the foregoing equation andthen eliminating θ, the following equation is obtained:V _(n) ⁴−2·r·P _(n) ·V _(n) ²−2·x·Q _(n) ·V _(n) ²+(r ² +x ²)·(P _(n) ²+Q _(n) ²)−V _(n) ² ·V _(g) ²=0

The foregoing equation is represented in matrix form as:

$V_{n}^{4} = {\left\lbrack {{2 \cdot P_{n} \cdot V_{n}^{2}} - {{r \cdot \left( {P_{n}^{2} + Q_{n}^{2}} \right)}{2 \cdot Q_{n} \cdot V_{n}^{2}}} - {{x \cdot \left( {P_{n}^{2} + Q_{n}^{2}} \right)}V_{n}^{2}}} \right\rbrack\begin{bmatrix}r \\x \\V_{g}^{2}\end{bmatrix}}$

Next, the three matrices Yn, Hn, and U are defined as shown below:

$\begin{matrix}{Y_{n} = V_{n}^{4}} \\{H_{n} = \begin{bmatrix}{{2 \cdot P_{n} \cdot V_{n}^{2}} - {{r \cdot \left( {P_{n}^{2} + Q_{n}^{2}} \right)}{2 \cdot}}} \\{{Q_{n} \cdot V_{n}^{2}} - {{x \cdot \left( {P_{n}^{2} + Q_{n}^{2}} \right)}V_{n}^{2}}}\end{bmatrix}} \\{U = \begin{bmatrix}r \\x \\V_{g}^{2}\end{bmatrix}}\end{matrix}$Next, a least squares estimation technique known to those skilled in theart is utilized to determine the unknown parameter values (r, x, andV_(g)). For example, a batch mode equation can be utilized to determinethe unknown parameter values (r, x, and Vg), as shown below:

$U_{k} = {\left\lbrack {\sum\limits_{n = 1}^{k}\;{H_{n}^{T} \cdot H_{n}}} \right\rbrack^{- 1}{\sum\limits_{n = 1}^{k}\;{H_{n}^{T} \cdot Y_{n}}}}$

It should be noted that since r and x also appear in the H_(n) term, aniterative solution is required. In general, a small random disturbancesignal injection is required for convergence of the solution for theparameter values (r, x, and Vg). It should be further noted that othermathematical techniques such as recursive estimation techniques andKalman filtering to achieve an optimal tracking of parameters in thepresence of noise can be utilized.

Referring to FIGS. 12 and 13, a plot 40 illustrates convergence of thereactance value (x) associated with the electrical grid 12, byiteratively calculating (U_(k)). Further, a plot 141 illustratesconvergence of the resistance (r) of the electrical grid 12, byiteratively calculating (U_(k)). Finally, the plot 142 illustratesconvergence of the voltage level (Vg), by iteratively calculating(U_(k)).

Referring to FIG. 11, a method for determining parameter valuesassociated with the electrical grid 12 utilizing the main controller 32and the measurement device 30 will be explained. The method can beimplemented utilizing software algorithms stored in a computer storagemedium executed by the main controller 32.

At step 130, the measurement device 30 transmits a first plurality ofsignals indicative of real power levels (Pn) at the point ofinterconnection 19 of the wind farm 11 to the electrical grid 12, to themain controller 32.

At step 132, the measurement device 30 transmits a second plurality ofsignals indicative of reactive power levels (Qn) at the point ofinterconnection 19, to the main controller 32.

At step 134, the measurement device 30 transmits a third plurality ofsignals indicative of voltage levels (Vn) at the point ofinterconnection 19, to the main controller 32.

At step 136, the main controller 32 receives the first, second, andthird plurality of signals and determines a plurality of real powervalues (Pn), a plurality of reactive power values (Qn), and a pluralityof voltage levels (Vn), respectively, therefrom.

At step 138, the main controller 32 estimates at least one parameterassociated with the electrical grid 12 utilizing the plurality of realpower values (Pn), the plurality of reactive power values (Qn), and theplurality of voltage values (Vn), and a mathematical estimationtechnique. For example, the parameter values (r, x, and Vg) can bedetermined utilizing the plurality of real power values (Pn), theplurality of reactive power values (Qn), and the plurality of voltagevalues (Vn) and the mathematical equations described above.

The inventive system, method, and article of manufacture for controllingoperation of a wind farm provide a substantial advantage over othersystem and methods. In particular, system, method, and article ofmanufacture provide a technical effect of estimating parameter valuesassociated with an electrical grid utilizing measured values at a pointof interconnection between a wind farm and an electrical grid.

The above-described methods can be embodied in the form of computerprogram code containing instructions embodied in tangible media, such asfloppy diskettes, CD ROMs, hard drives, or any other computer-readablestorage medium, wherein, when the computer program code is loaded intoand executed by a computer, the computer becomes an apparatus forpracticing the invention.

While the invention is described with reference to an exemplaryembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalence may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to the teachings of theinvention to adapt to a particular situation without departing from thescope thereof. Therefore, it is intended that the invention not belimited to the embodiment disclosed for carrying out this invention, butthat the invention includes all embodiments falling with the scope ofthe intended claims. Moreover, the use of the term's first, second, etc.does not denote any order of importance, but rather the term's first,second, etc. are used to distinguish one element from another.

1. A method for determining parameter values associated with anelectrical grid, the electrical grid having a point of interconnectionwhere the electrical grid is electrically coupled to a power source, themethod comprising: measuring real power at the point of interconnectionof the electrical grid to obtain a plurality of real power values;measuring reactive power at the point of interconnection of theelectrical grid to obtain a plurality of reactive power values;measuring a voltage at the point of interconnection of the electricalgrid to obtain a plurality of voltage values; estimating at least oneparameter value associated with the electrical grid utilizing theplurality of real power values, the plurality of reactive power values,and the plurality of voltage values, and a mathematical estimationtechnique; and controlling operation of a wind turbine to generateelectrical power to the electrical grid based on the at least oneestimated parameter value.
 2. The method of claim 1, wherein the atleast one estimated parameter value associated with the electrical gridcomprises at least one of an electrical line resistance value, anelectrical line reactance value, and a grid voltage value.
 3. The methodof claim 1, wherein the mathematical estimation technique comprises aleast-squares estimation technique.
 4. A system for determiningparameter values associated with an electrical grid, the electrical gridhaving a point of interconnection where the electrical grid iselectrically coupled to a power source, the system comprising: ameasurement device configured to measure real power at the point ofinterconnection of the electrical grid to obtain a plurality of realpower values, the measurement device further configured to measurereactive power at the point of interconnection of the electrical grid toobtain a plurality of reactive power values, the measurement devicefurther configured to measure a voltage at the point of interconnectionof the electrical grid to obtain a plurality of voltage values; and acontroller operably communicating with the measurement device, thecontroller configured to estimate at least one parameter valueassociated with the electrical grid utilizing the plurality of realpower values, the plurality of reactive power values, and the pluralityof voltage values, and a mathematical estimation technique.
 5. Thesystem of claim 4, wherein the at least one estimated parameter valueassociated with the electrical grid comprises at least one of anelectrical line resistance value, an electrical line reactance value,and a grid voltage value.
 6. The system of claim 4, wherein themathematical estimation technique comprises a least-squares estimationtechnique.
 7. An article of manufacture, comprising: a computer storagemedium having a computer program encoded therein for determiningparameters values associated with an electrical grid, the electricalgrid having a point of interconnection where the electrical grid iselectrically coupled to a power source, the computer storage mediumcomprising: code for measuring real power at the point ofinterconnection of the electrical grid to obtain a plurality of realpower values; code for measuring reactive power at the point ofinterconnection of the electrical grid to obtain a plurality of reactivepower values; code for measuring a voltage at the point ofinterconnection of the electrical grid to obtain a plurality of voltagevalues; and code for estimating at least one parameter value associatedwith the electrical grid utilizing the plurality of real power values,the plurality of reactive power values, and the plurality of voltagevalues, and a mathematical estimation technique.
 8. The article ofmanufacture of claim 7, wherein the at least one estimated parametervalue associated with the electrical grid comprises at least one of anelectrical line resistance value, an electrical line reactance value,and a grid voltage value.
 9. The article of manufacture of claim 7,wherein the mathematical estimation technique comprises a least-squaresestimation technique.